Can anyone tell me the difference between the Garmin Edge models? For instance - what is the difference between a 520 and a 530? I think that one of mine is an 830 and it has a lot of buttons on it and is a pain-in-the-butt to get working though the basic software appears to be the same thing. There are several probably Chinese copies some of which seem to have a better program and display as well as a longer battery life. But they don't connect to a Garmin mount and the one's they provide don't work for integrated bar/stem combos. The Garmins have absolutely terrible screen contrast and most of the time wearing sunglasses I can barely make out the speed leg alone the mileage. I will say that I really like the rear wheel placement of the speed and cadence mechanism I can't think of any possible worse position for a speed pickup that a front wheel But I may be biased since that is partially how I got my concussion.